1. Field of the Invention
The present invention relates to a toner conveyance member for conveying toner in an electrophotographic image forming apparatus, as well as a developing device and an image forming apparatus using the same.
2. Description of Related Art
For example, the toner conveyance member is provided as a supply screw or a stirring screw in a developing device included in an electrophotographic image forming apparatus, as described in Japanese Patent Laid-Open Publication No. 2006-337817.
More specifically, the developing device has a developer (e.g., a two-component developer) stored in a developer container. The developer container includes a developing roller horizontally disposed near a photoreceptor drum so as to be approximately parallel to the photoreceptor drum. When the developing roller rotates, the developer in the developer container is conveyed and supplied to a developing area on the photoreceptor drum while being carried on the outer circumferential surface of the developing roller.
Provided almost directly below the developing roller is a supply screw. The supply screw is horizontally disposed near the developing roller in the developer container so as to be approximately parallel to the developing roller. Moreover, provided diagonally below the supply screw is a stirring screw. The stirring screw is disposed horizontally in the developer container so as to be approximately parallel to the supply screw with a partition extending along the supply screw between the stirring screw and the supply screw.
A conventional toner conveyance member will be described in detail below with reference to FIG. 12. In FIG. 12, the toner conveyance member 101 includes a shaft 102, a blade member 103, and paddle members 104.
The blade member 103 is a helical fin winding around the outer circumferential surface of the shaft 102 in the direction of arrow θ2 (also referred to below as the “rotational direction θ2” or simply as the “direction θ2”), and the fin continues to extend helically in the axial direction y of the shaft 102.
The paddle members 104 are in the form of plates protruding approximately perpendicularly from the outer circumferential surface of the shaft 102 and extending in the axial direction y. Moreover, the entire end of each paddle member 104 in the axial direction y is connected to the blade member 103.
In the case of the toner conveyance member 101 thus configured, once the shaft 102 rotates, the blade member 103 conveys the developer in the opposite direction to the axial direction y. Moreover, the paddle members 104 move and stir the developer in the rotational direction θ2 of the shaft 102.
However, the conventional toner conveyance member 101 has a problem of being prone to toner aggregation. More specifically, as shown in a dotted circle in FIG. 12, there are two spaces defined by the shaft 102, the blade member 103, and the paddle member 104, and one of the spaces that is positioned forward in the rotational direction θ2 with respect to the paddle member 104 is referred to as a recess 105. Once toner T enters the recess 105 (see the hatched portion in the figure), the toner T is unlikely to move out of the recess 105 due to the paddle member 104 rotating in the rotational direction θ2. Accordingly, the toner T in the recess 105 keeps receiving pressure for a prolonged period of time, resulting in aggregation of the toner T.